Method and apparatus for contention-based channel access with directional antenna over wideband high frequency wireless system

ABSTRACT

Provided are a method of performing contention based channel access by classifying a contention period into a beamformable contention period in which a beamforming is allowed and a non-beamformable contention period in which the beamforming is interrupted so as to resolve an issue regarding channel access occurring due to an introduction of a directional antenna for handling a path loss in a wideband wireless communication system according to an embodiment of the present invention, and a method for maximizing a spatial reuse gain by managing, for each direction, information about a transmission time of a message received from a dispersion device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No.10-2010-0096190, filed on Oct. 4, 2010 and No. 10-2011-0083893, filed onAug. 23, 2011, in the Korean Intellectual Property Office, thedisclosures of which are incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to a method for resolving an issueregarding channel access due to an introduction of a directional antennafor handling a path loss, and maximizing a spatial reuse gain in awireless communication system in which data may be transmitted at arelatively high speed through use of an ultra-wideband frequency band.

2. Description of the Related Art

A Carrier Sense Multiple Access with Contention Avoidance (CSMA/CA)scheme for a wireless local area network (LAN) system using a frequencyband of 2.4 GHz or 5 GHz has been developed on the assumption of usingan omnidirectional antenna and thus, may involve several issues when adirectional antenna is used. A transmission through the directionalantenna may concentrate a signal in a predetermined direction, therebyextending a signal reach distance in comparison with the omnidirectionalantenna, and may enable concurrent communication in different directionsusing a spatial reuse gain. However, a system performance maydeteriorate due to increases in a deafness issue and a hidden nodeissue. Even though the hidden node issue may occur when theomnidirectional antenna is used, the hidden node issue may beeffectively resolved by transmitting a ready to send (RTS) control frameand a clear to send (CTS) control frame before exchanging aDATA/acknowledgement (ACK) packet.

Here, a deafness issue may refer to a state in which a reception nodefails to receive an RTS control frame of a transmission node. When areception node fails to receive an RTS control frame of a transmissionnode, the node transmitting the RTS control frame may attemptretransmission of the RTS control frame. In this instance, thetransmission node may double a contention window of the transmissionnode according to a CSMA/CA protocol, thereby delaying a channel accesstime. Due to a continuous deafness, data packets to be transmitted maybe deleted in a repeated manner.

The hidden node issue may refer to an issue of degrading a systemperformance due to packets including an RTS control frame that createerrors in communication occurring around the corresponding node. Here,the packets may be transmitted by the corresponding node not recognizingcommunication occurring around the corresponding node.

Nowadays, a millimeter wave communication system based on a 60 GHzfrequency band is being developed on the assumption of using adirectional antenna due to a millimeter wave propagation characteristic.The millimeter wave communication system may perform a beamformingprocess to set a link to a destination device when the directionalantenna is used. The beamforming process may correspond to a process ofgenerating a plurality of beams being used in a predetermined area,identifying a predetermined destination device by transmitting signalsin all directions, successively using beams, and then forming a link fora data transmission by forming relatively delicate beams. The millimeterwave communication system recognizing a CSMA/CA issue occurring when adirectional antenna is used may schedule a time division multiple access(TDMA) resource allocation using a central control unit such as anaccess point (AP), and may enable device pairs predetermined in ascheduled TDMA resource to communicate, thereby resolving the CSMA/CAissue. However, when traffic is generated intermittently, a TDMA schememay not use resources effectively and thus, the TDMA scheme may be usedin combination with a CSMA/CA scheme. To effectively apply the CSMA/CAscheme to the millimeter wave communication system, a spatial reuse gainmay be maximized while resolving issues described in the foregoing.

SUMMARY

An aspect of the present invention provides an apparatus and method forcontention based channel access using a directional antenna in awideband wireless communication system.

Another aspect of the present invention also provides a central processdevice in a wideband wireless communication system for generating andtransmitting a beacon message that includes information about abeamformable contention period and a non-beamformable contention period.

Still another aspect of the present invention also provides a dispersiondevice in a wideband wireless communication system that performs abeamforming in a beamformable contention period and performscommunication in a non-beamformable contention period.

Yet another aspect of the present invention also provides a method andapparatus for devising an effective Carrier Sense Multiple Access withContention Avoidance (CSMA/CA) communication scheme through help of acentral control unit such as a base station, and enhancing a spatialreuse gain using a the CSMA/CA communication scheme in a system allowingbeamforming and high-speed communication using a directional antenna anda millimeter wave including a 60 GHz frequency band.

According to an aspect of the present invention, there is provided acentral control unit for providing contention based channel access in awideband wireless communication system, the central control unitincluding an information collector to receive, from dispersion devicesin a network, information about participating in a contention period andinformation related to setting a receiving antenna, a source allocationscheduling unit to allocate a resource by dividing the contention periodinto a beamformable contention period corresponding to a contentionperiod in which a beamforming of a directional antenna is allowed and anon-beamformable contention period corresponding to a contention periodin which the beamforming is interrupted, and a beacon generator togenerate a beacon message including information about the beamformablecontention period and the non-beamformable contention period, and totransmit the beacon message to the dispersion devices.

According to another aspect of the present invention, there is provideda dispersion device for providing contention based channel access in awideband wireless communication system, the central control unitincluding a requesting unit to request a central control unit toparticipate in a contention period, a beacon processing unit to verify,in a beacon message received from the central control unit, abeamformable contention period corresponding to a contention period inwhich a beamforming is allowed and a non-beamformable contention periodcorresponding to a contention period in which the beamforming isinterrupted, a beamforming unit to perform beamforming with a dispersiondevice to communicate in the beamformable contention period, and a dataprocessing unit to process data transmitted to and received from thedispersion device to communicate in the non-beamformable contentionperiod through a beam formed by the beamforming unit.

According to still another aspect of the present invention, there isprovided a dispersion device for providing contention based channelaccess in a wideband wireless communication system, the central controlunit including a direction detector to measure a receiving direction ofa directional signal received during an omnidirectional receivingantenna mode, a duration controller to manage, for each predetermineddirection, information of a transmission duration corresponding to anetwork allocation vector included in a message that is wirelesslyreceived in a state set to the omnidirectional receiving antenna mode,and a media access control (MAC) layer unit to start communication wheninformation of a transmission duration of a predetermined directionmanaged by the duration controller is “0” by verifying the informationof the transmission duration of the predetermined direction forcommunication in the predetermined direction.

According to yet another aspect of the present invention, there isprovided a method of providing contention based channel access in acentral control unit of a wideband wireless communication system, themethod including receiving, from dispersion devices in a network,information about participating in a contention period and informationrelated to setting a receiving antenna, allocating a resource bydividing the contention period into a beamformable contention periodcorresponding to a contention period in which a beamforming of adirectional antenna is allowed and a non-beamformable contention periodcorresponding to a contention period in which the beamforming isinterrupted, and generating a beacon message including information aboutthe beamformable contention period and the non-beamformable contentionperiod, and transmitting the beacon message to the dispersion devices.

According to further another aspect of the present invention, there isprovided a method of providing contention based channel access in adispersion device of a wideband wireless communication system, themethod including requesting a central control unit to participate in acontention period, verifying, in a beacon message received from thecentral control unit, a beamformable contention period corresponding toa contention period in which a beamforming is allowed and anon-beamformable contention period corresponding to a contention periodin which the beamforming is interrupted, performing beamforming with adispersion device to communicate in the beamformable contention period,and exchanging data with the dispersion device to communicate in thenon-beamformable contention period through a beam formed by performingthe beamforming.

According to embodiments of the present invention, it is possible tolimit, to a beamformable contention period, interference betweenadjacent devices occurring during a beamforming operation, and enabledevices to perform communication in a more effective contention schemeusing a central control unit that divides a contention period into abeamformable contention period and a non-beamformable contention periodand allocates the divided contention period. According to embodiments ofthe present invention, it is possible to enhance a rate of channel useby providing a relatively large amount of information to devicesparticipating in a contention period so as to reduce unsuccessfulattempts at communication using a dispersion device that informs acentral control unit about information as to whether to participate inthe contention period and related to setting a receiving antenna duringa participation. According to embodiments of the present invention, itis possible to enhance a number of concurrent transmissions, throughspatial reuse, using a dispersion device that manages and setsinformation of a transmission duration for each direction recognized bythe dispersion device.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects, features, and advantages of the inventionwill become apparent and more readily appreciated from the followingdescription of exemplary embodiments, taken in conjunction with theaccompanying drawings of which:

FIG. 1 is a diagram illustrating a configuration of a wideband wirelesscommunication system according to embodiments of the present invention;

FIG. 2 is a diagram illustrating an example of a superframe used in awideband wireless communication system according to embodiments of thepresent invention;

FIG. 3 is a diagram illustrating a signal reach distance formed bysetting an antenna according to embodiments of the present invention;

FIG. 4 is a diagram illustrating a sector sweep for transmitting andreceiving an omnidirectional signal using a directional antennaaccording to embodiments of the present invention;

FIG. 5 is a diagram illustrating an example of a superframe including abeamformable contention period and a non-beamformable contention periodaccording to embodiments of the present invention;

FIG. 6 is a block diagram illustrating a configuration of a centralcontrol unit for providing contention based channel access in a widebandwireless communication system according to embodiments of the presentinvention;

FIG. 7 is a block diagram illustrating a configuration of a dispersiondevice for providing contention based channel access in a widebandwireless communication system according to embodiments of the presentinvention;

FIG. 8 is a flowchart illustrating a method for providing contentionbased channel access in a central control unit of a wideband wirelesscommunication system according to embodiments of the present invention;

FIG. 9 is a flowchart illustrating a method for providing contentionbased channel access in a dispersion device of a wideband wirelesscommunication system according to embodiments of the present invention;

FIG. 10 is a diagram illustrating an example of communication in whichspatial reuse is allowed according to embodiments of the presentinvention; and

FIG. 11 is a diagram illustrating a configuration of a dispersion devicethat manages information of a transmission duration for each directionaccording to embodiments of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. Exemplary embodiments are described below to explain thepresent invention by referring to the figures.

FIG. 1 is a diagram illustrating a configuration of a wideband wirelesscommunication system according to embodiments of the present invention.

Referring to FIG. 1, in a wideband wireless communication system wherediscrete dispersion devices 120 through 160 wirelessly exchange signals,a single central control unit 110 may perform a resource allocation anda time synchronization between devices, and the dispersion devices 120through 160 may use a system architecture performing communication basedon information of the time synchronization and the resource allocationsignaled by the central control unit 110.

The system architecture according to embodiments of the presentinvention may be similar to a common cellular network and a wirelesslocal area network (LAN) having an access point (AP). However, whilecommunication is performed between a terminal and a base station orbetween a terminal and an AP in the cellular network and the wirelessLAN having an AP, communication may be performed directly betweendispersion devices in a wireless architecture based on the presentinvention. Further, while signals transmitted by a single device arepropagated in all directions in a conventional cellular network andwireless LAN system, the present invention is based on a wireless deviceusing a directional antenna so that a data communication signal may bepropagated in a predetermined direction by performing a beamforming toenhance a transmitting and receiving antenna gain.

The central control unit 110 of FIG. 1 may share the information of thetime synchronization and the resource allocation with devices bytransmitting a beacon message to all devices, thereby forming acommunication structure illustrated in FIG. 2.

FIG. 2 is a diagram illustrating an example of a superframe used in awideband wireless communication system according to embodiments of thepresent invention.

A central control unit may load a beacon message with information of atime synchronization and information of a time resource allocation, anddeliver the beacon message to all devices. The central control unit mayrepeatedly transmit beacon messages based on a number of supportedsectors. Dispersion devices may set a receiving antenna to have as widebeam width as possible so as to receive a beacon message. In thisinstance, the beam having a wide width may be referred to as aQuasi-omni reception beam. Since the beacon message includes significantinformation, and receiving antenna gains of reception devices arerelatively low, a relatively reliable modulation and coding scheme (MCS)may be used. The beacon message may include allocation information of atime resource indicating an access period, allocation information of atime resource indicating a polling period, and allocation information ofa time resource indicating a data transmission period. The access periodmay correspond to a period in which devices receiving a beacon in abeacon transmission period perform a beamforming with a central controlunit, thereby enhancing a transmitting antenna gain. A dispersion devicemay repeatedly transmit a message for a beamforming to the centralcontrol unit in the access period, thereby aligning a beam to thecentral control unit. In this instance, the dispersion device may informthe central control unit about beam information of the central controlunit acquired through receiving the beacon message, thereby informingthe central control unit about beam information to be used when thecentral control unit transmits a message to the corresponding device.The polling period may correspond to a time period in which the centralcontrol unit transmits a message to a predetermined device, and a devicereceiving the message transmits a message to the central control unit inresponse to the reception. The data transmission period may include timeresource periods in which dispersion devices and the central controlunit may communicate with each other. The data transmission period mayinclude a contention period available to all devices and a scheduleperiod available to predetermined transmission and reception devices,and at least one contention period and at least one schedule period maybe included.

The data transmission period may include only contention periods, mayinclude only schedule periods, and may include a combination of thecontention period and the schedule period as illustrated in FIG. 2. Inthe data transmission period, a beam alignment may be performed betweendispersion devices by performing a beamforming between dispersiondevices, and then data may be transmitted and received. A transmissiondevice and a reception device performing a beamforming may changesettings of a transmitting antenna and a receiving antenna,respectively. An antenna gain value may vary depending on a setting ofan antenna and thus, a transmission and reception distance of a signalmay vary.

FIG. 3 is a diagram illustrating a signal reach distance formed bysetting an antenna according to embodiments of the present invention.

Referring to FIG. 3, the signal reach distance may increase as anantenna setting is changed from an omni direction to a sector, and to abeam level. Here, the omni direction may correspond to an omni datacoverage area 320 and an omni control coverage area 330, the sector maycorrespond to a sector coverage area 340, and the beam level maycorrespond to a fine-beam coverage area 350. When an antenna is set tothe omni direction, the signal reach distance may vary depending on anMCS value. Here, the omni control coverage area 330 indicates a distancewhere a control message, to which a relatively reliable MCS is applied,reaches, and the omni data coverage area 320 indicates a distance wheretransmitted data reaches.

A dispersion device 310 may have a longest communication distance whenusing the fine-beam coverage area 350. When communication is performedat a predetermined distance, and a transmission device and a receptiondevice are properly aligned, a fine-beam may acquire a relativelyexcellent communication quality. However, when the fine-beam is used, asignal may be delivered to a device at a position to which a directionalbeam fails to be directed. Thus, a dispersion device to communicate maybe identified prior to a fine-beam setting through a beamforming. Toidentify the dispersion device, a dispersion device 410 of FIG. 4 mayuse a sector sweep scheme of transmitting a control signal for abeamforming successively using all separate sectors among supportedsectors.

FIG. 4 is a diagram illustrating a sector sweep for transmitting andreceiving an omnidirectional signal using a directional antennaaccording to embodiments of the present invention.

When a transmission dispersion device performs a sector sweep, areception dispersion device may attempt to receive signals in alldirections, and may successively use reception sectors as an alternativeto. As a result, the reception dispersion device may recognize sectorinformation, which may be referred to as an optimal transmission sector,having a relatively excellent reception signal quality, and may allowthe transmission dispersion device to determine a sector to be used byfeeding back the sector information. When feeding back the optimaltransmission sector, a transmission and reception device may change afunction, and perform the sector sweep. As a result, a communicationdevice may determine an optimal sector used for communication with anopponent device. A scheme of determining a fine-beam may be similar tothe sector sweep scheme.

The operation of performing a sector sweep and determining a fine-beammay be referred to as a beamforming operation. The beamforming operationmay be performed in a schedule period or a contention period. To performthe beamforming operation in a schedule period, a dispersion devicestarting a beamforming operation may request a central control unit fora schedule period, and may use an allocated schedule period. In thisinstance, two dispersion devices performing the beamforming operationmay correspond to devices communicating in the allocated scheduleperiod. In the contention period in which the central control unitpermits all dispersion devices desiring to communicate to access thecentral control unit, communication may be performed through acontention based on a Carrier Sense Multiple Access with ContentionAvoidance (CSMA/CA) scheme. When omnidirectional communication isperformed, simultaneous transmissions by at least two dispersion devicesmay cause a collision. However, when a sector or a fine-beam is used, acollision may be avoided depending on a direction of delivering a signaleven though simultaneous transmissions occur. When a dispersion devicetransmitting a signal in the contention period does not perform abeamforming with a destination dispersion device, the sector sweepillustrated in FIG. 4 may be performed, which may significantlyinterfere with other dispersion devices. Further, in the contentionperiod, dispersion devices at a transmission end and at a reception endmay not verify each other, and whether the opponent prepares forcommunication. Also, the devices may not be informed of a receivingantenna setting of the opponent, which may not be an issue for theschedule period since the central control unit may designate atransmission and reception dispersion device of the correspondingschedule period through a message such as a beacon.

Accordingly, according to embodiments of the present invention, thecentral control unit may allocate a beamformable contention periodcorresponding to a contention period during which a beamformingincluding a sector sweep operation is allowed and a non-beamformablecontention period corresponding to a contention period during which thebeamforming is interrupted as illustrated in FIG. 5. In thenon-beamformable contention period, dispersion devices may attemptaccess upon completing a beamforming.

FIG. 5 is a diagram illustrating an example of a superframe including abeamformable contention period and a non-beamformable contention periodaccording to embodiments of the present invention.

A device desiring to perform a beamforming may receive an allocation ofa schedule period and perform the beamforming, or may perform thebeamforming in the beamformable contention period. By classifying acontention period into the beamformable contention period and thenon-beamformable contention period, communication efficiency may beenhanced in the non-beamformable contention period. A central controlunit may continuously dispose a beamformable contention period and anon-beamformable contention period in a data transmission period, andmay schedule one of a beamformable contention period and anon-beamformable contention period as necessary. Various schemes may beused to signal to all devices by classifying contention periods into abeamformable contention period and a non-beamformable contention period,and a basic scheme may classify contention periods using “0” and “1” byadding one-bit information.

A signaling of the central control unit may be used to identify anantenna setting of reception dispersion devices participating in acontention period. A dispersion device participating in a contentionperiod may report, to the central control unit, a receiving antenna modeset in the contention period in advance. When the central control unitsignals an allocation of a contention period, the central control unitmay also signal a receiving antenna setting of each of dispersiondevices participating in the corresponding contention period.Information about a receiving antenna setting reported by apredetermined dispersion device participating in a contention period maybe set in a varied manner, and may be indicated by a sector number asillustrated in FIG. 4. A dispersion device performing a beamforming withthe predetermined dispersion device may recognize an antenna setting ofa dispersion device indicated by a sector number and thus, may determinewhether communication with a dispersion device having an indicatedsector number in a contention period is allowed, and may determine atransmission sector or a fine-beam to be used for communication.

The central control unit may transmit, to dispersion devices, acontention period participation list including information aboutdispersion devices participating in a contention period and informationrelated to setting a receiving antenna for each of the dispersiondevices participating in the contention period. In this instance, thecontention period participation list may be included in a message, forexample, a beacon transmitted to all devices by the central controlunit, and the message including the contention period participation listmay be transmitted to a dispersion device. The dispersion deviceacquiring the contention period participation list may verify dispersiondevices waiting for a reception in the corresponding contention period,and information related to setting a receiving antenna for thedispersion devices.

A configuration of a central control unit and a dispersion deviceaccording to embodiments of the present invention will be described withreference to FIG. 6 and FIG. 7.

FIG. 6 is a block diagram illustrating a configuration of a centralcontrol unit 600 for providing contention based channel access in awideband wireless communication system according to embodiments of thepresent invention. Referring to FIG. 6, the central control unit 600includes an information collector 610, a source allocation schedulingunit 620, and a beacon generator 630.

The information collector 610 may receive, from dispersion devices in anetwork, information about participating in a contention period andinformation related to setting a receiving antenna.

The source allocation scheduling unit 620 may schedule a datatransmission period including at least one of a beamformable contentionperiod, a non-beamformable contention period, and a schedule periodbased on a request for a resource from the dispersion devices. In thisinstance, the source allocation scheduling unit 620 may allocate aresource by dividing the contention period into the beamformablecontention period corresponding to a contention period in which abeamforming of a directional antenna is allowed and the non-beamformablecontention period corresponding to a contention period in which thebeamforming is interrupted.

The beacon generator 630 may generate a beacon message includinginformation about the beamformable contention period and thenon-beamformable contention period, and may transmit the beacon messageto the dispersion devices.

The beacon message may include allocation information of a time resourceindicating an access period, allocation information of a time resourceindicating a polling period, and allocation information of a timeresource indicating a data transmission period. The data transmissionperiod may include at least one of the beamformable contention period,the non-beamformable contention period, and the schedule period.

The beacon message may further include a contention period participationlist including information about dispersion devices participating in thecontention period and information related to setting a receiving antennafor each of the dispersion devices participating in the contentionperiod.

All of the information collector 610, the source allocation schedulingunit 620, and the beacon generator 630 may be included in a media accesscontrol (MAC) layer of the central control unit 600.

FIG. 7 is a block diagram illustrating a configuration of a dispersiondevice 700 for providing contention based channel access in a widebandwireless communication system according to embodiments of the presentinvention. Referring to FIG. 7, the dispersion device 700 includes arequesting unit 710, a beacon processing unit 720, a beamforming unit730, and a data processing unit 740.

The requesting unit 710 may request a central control unit toparticipate in a contention period. The requesting unit 710 may inform acentral control unit of information related to setting a receivingantenna for the dispersion device when the requesting unit 710 requestsparticipation in the contention period.

The beacon processing unit 720 may verify, in a beacon message receivedfrom the central control unit, a beamformable contention periodcorresponding to a contention period in which a beamforming is allowedand a non-beamformable contention period corresponding to a contentionperiod in which the beamforming is interrupted. The beacon processingunit 720 may verify, in the beacon message, a contention periodparticipation list including information about dispersion devicesparticipating in the contention period and information related tosetting a receiving antenna for each of the dispersion devicesparticipating in the contention period.

The beamforming unit 730 may perform beamforming with a dispersiondevice to communicate in the beamformable contention period. Thebeamforming unit 730 may perform a beamforming by verifying informationrelated to setting a receiving antenna for the dispersion device tocommunicate in the contention period participation list.

The data processing unit 740 may process data transmitted to andreceived from the dispersion device to communicate in thenon-beamformable contention period through a beam formed by thebeamforming unit 730.

The requesting unit 710, the beacon processing unit 720, the beamformingunit 730, and the data processing unit 740 may all be included in a MAClayer of the dispersion device 700.

Hereinafter, a method for contention based channel access using adirectional antenna in a wideband wireless communication systemaccording to embodiments of the present invention will be described withreference to FIG. 8 and FIG. 9.

FIG. 8 is a flowchart illustrating a method for providing contentionbased channel access in a central control unit of a wideband wirelesscommunication system according to embodiments of the present invention.

Referring to FIG. 8, in operation 810, the central control unitreceives, from dispersion devices in a network, information aboutparticipating in a contention period and information related to settinga receiving antenna.

In operation 820, the central control unit schedules a data transmissionperiod including at least one of a beamformable contention period, anon-beamformable contention period, and a schedule period based on arequest for a resource from the dispersion devices. In this instance,the central control unit may allocate a resource by dividing thecontention period into the beamformable contention period correspondingto a contention period during which a beamforming of a directionalantenna is allowed and the non-beamformable contention periodcorresponding to a contention period during which the beamforming isinterrupted.

In operation 830, the central control unit generates a beacon messageincluding information about the beamformable contention period and thenon-beamformable contention period, and transmits the beacon message tothe dispersion devices.

FIG. 9 is a flowchart illustrating a method for providing contentionbased channel access in a dispersion device of a wideband wirelesscommunication system according to embodiments of the present invention.

Referring to FIG. 9, in operation 910, the dispersion device requests acentral control unit to participate in a contention period. In thisinstance, the dispersion device may inform a central control unit ofinformation related to setting a receiving antenna for the dispersiondevice.

In operation 912, the dispersion device verifies information related toa resource allocation by receiving a beacon message from the centralcontrol unit.

In operation 914, the dispersion device verifies whether a beamformingis necessary.

When the beamforming is necessary as a result of the verification inoperation 914, the dispersion device verifies whether a beamformablecontention period is included in a data transmission period of asuperframe in operation 916.

When the beamformable contention period is verified to be included inthe data transmission period as a result of operation 916, thedispersion device performs a beamforming with a dispersion device tocommunicate in operation 918, and returns to operation 910. In thisinstance, when the beamformable contention period is excluded as aresult of the verification in operation 916, the dispersion devicereturns to operation 910.

When the beamforming is not necessary since a beamforming is previouslycompleted as a result of the verification in operation 914, thedispersion device verifies whether a non-beamformable contention periodis included in the data transmission period of the superframe inoperation 920.

When the non-beamformable contention period is excluded as a result ofthe verification in operation 920, the dispersion device returns tooperation 910.

When the non-beamformable contention period is verified to be includedin the data transmission period as a result of operation 920, thedispersion device verifies information related to whether a dispersiondevice to communicate participates in the contention period andinformation related to setting a receiving antenna for the dispersiondevice to communicate in operation 922.

In operation 924, the dispersion device verifies whether the dispersiondevice is allowed to communicate with the dispersion device based oninformation verified in operation 924.

When the dispersion device is allowed to communicate as a result of theverification in operation 924, the dispersion device performscommunication with the dispersion device to communicate in operation926. When the dispersion device is not allowed to communicate as aresult of the verification in operation 924, the dispersion device waitsin a reception mode in operation 928.

The present invention may provide a method for enhancing a number ofconcurrent transmissions through spatial reuse in the contention period.The dispersion device may operate using a CSMA/CA scheme in thecontention period, and a network allocation vector (NAV) variable may bemanaged to avoid a collision due to a concurrent transmission. Here, theNAV variable may be used to determine whether a channel is occupied byanother device, and to determine a period of time during which thechannel is occupied. The NAV variable may be set to a packet lengthvalue in a time unit recorded in a header of a received packet, and theNAV variable, as a type of information of a transmission duration, maycorrespond to a duration field value within a MAC header of a receivedmessage.

For omnidirectional communication, the dispersion device may have asingle NAV variable, and may set a duration field value of a receivedpacket to an NAV variable value. The dispersion device may decrease theNAV variable value over time, and may delay a channel access until apoint in time at which the NAV variable value becomes “0.”

However, for directional communication, the dispersion device may starta transmission when the NAV variable value does not correspond to “0.”Depending on a communication direction, the dispersion device may starta transmission when the NAV variable value exceeds “0.”

Starting a transmission when the NAV variable value does not correspondto “0” will be described with reference to FIG. 10.

FIG. 10 is a diagram illustrating an example of communication in whichspatial reuse is allowed according to embodiments of the presentinvention.

Referring to FIG. 10, when it is assumed that a dispersion device (C)1030, among four dispersion devices (A through D) 1010 through 1040participating in a contention period, has an omnidirectional receivingantenna setting, the dispersion device (C) 1030 may set an NAV value bya packet received through a communication link between the dispersiondevice (A) 1010 and the dispersion device (B) 1020. In this instance, adirection of receiving a packet through a communication link between thedispersion device (A) 1010 and the dispersion device (B) 1020 maycorrespond to a sector direction 4 of the dispersion device (C) 1030.Thus, when the dispersion device (C) 1030 desires to communicate withthe dispersion device (D) 1040 in a sector direction 3, it may beefficient to start communication with the dispersion device (D) 1040without waiting for the NAV value to become “0” even though the NAVvalue is set to a value greater than “0” by the communication linkbetween the dispersion device (A) 1010 and the dispersion device (B)1020. Accordingly, the present invention suggests a device for managingNAV variables of a number of directions that may be regulated. The NAVvalues may be set for each direction of a received packet, andcommunication in a predetermined direction may be started when an NAVvalue in the predetermined direction corresponds to “0.”

FIG. 11 is a diagram illustrating a configuration of a dispersion devicethat manages information of a transmission duration for each directionaccording to embodiments of the present invention.

Referring to FIG. 11, the dispersion device includes a beamforming radiofrequency (RF) unit 1110, a physical layer unit 1120, a directiondetector 1130, a duration controller 1140, and an MAC layer unit 1150.

The beamforming RF unit 1110 may direct a transmission beam in apredetermined direction by adaptively changing phases and/or amplitudesof a plurality of power amplifiers (which may be referred to as anadaptive weight vector (AWV), and hereinafter referred to as atransmission AWV), and may direct a reception beam in a predetermineddirection by adaptively changing phases and/or amplitudes of a pluralityof low noise amplifiers (LNAs) (which may be referred to as a receptionAWV). The beamforming RF unit 1110 may support an omnidirectionalreception mode during a reception, and may receive information about atransmission and reception AWV from the MAC layer unit 1150 to direct atransmission and reception antenna in a predetermined direction.

The physical layer unit 1120 may correspond to a block performing amodulation and demodulation of a transmission and reception message anda coding and encoding of a channel, and may measure a quality of areception message.

The direction detector 1130 may measure a receiving direction of adirectional signal received during an omnidirectional receiving antennamode.

The duration controller 1140 may manage, for each predetermineddirection, information of a transmission duration corresponding to anetwork allocation vector included in a message that is wirelesslyreceived in a state set to the omnidirectional receiving antenna mode.In this instance, the duration controller 1140 may manage theinformation of the transmission duration along with a transmissionaddress of the received message, a reception address of the receivedmessage, and information of a receiving direction of the receivedmessage. The duration controller 1140 may verify the information of thetransmission duration in a duration field within a MAC header of thereceived message.

The MAC layer unit 1150 may control access to a wireless medium forgenerating and transmitting a message to be wirelessly transmitted, andfor analyzing a wirelessly received message. The MAC layer unit 1150 mayperform a transmission and reception using a CSMA/CA scheme, and maydeliver, to the beamforming RF unit 1110, an AWV corresponding toinformation related to an antenna setting for a transmission andreception to perform an antenna setting for the transmission andreception using the CSMA/CA scheme.

According to embodiments of the present invention, the MAC layer unit1150 may start communication when information of a transmission durationof a predetermined direction managed by the duration controller is “0”by verifying the information of the transmission duration of thepredetermined direction for communication in the predetermineddirection.

The above-described exemplary embodiments of the present invention maybe recorded in non-transitory computer-readable media including programinstructions to implement various operations embodied by a computer. Themedia may also include, alone or in combination with the programinstructions, data files, data structures, and the like. Examples ofnon-transitory computer-readable media include magnetic media such ashard disks, floppy disks, and magnetic tape; optical media such as CDROM discs and DVDs; magneto-optical media such as optical discs; andhardware devices that are specially configured to store and performprogram instructions, such as read-only memory (ROM), random accessmemory (RAM), flash memory, and the like. Examples of programinstructions include both machine code, such as produced by a compiler,and files containing higher level code that may be executed by thecomputer using an interpreter. The described hardware devices may beconfigured to act as one or more software modules in order to performthe operations of the above-described exemplary embodiments of thepresent invention, or vice versa.

Although a few exemplary embodiments of the present invention have beenshown and described, the present invention is not limited to thedescribed exemplary embodiments. Instead, it would be appreciated bythose skilled in the art that changes may be made to these exemplaryembodiments without departing from the principles and spirit of theinvention, the scope of which is defined by the claims and theirequivalents.

What is claimed is:
 1. A central control unit for providing contention based channel access in a wideband wireless communication system, the central control unit comprising: an information collector to receive, from dispersion devices in a network, information about participating in a contention period and information related to setting a receiving antenna; a source allocation scheduling unit to allocate a resource by dividing the contention period into a beamformable contention period corresponding to a contention period during which a beamforming of a directional antenna is allowed and a non-beamformable contention period corresponding to a contention period during which the beamforming is interrupted; and a beacon generator to generate a beacon message including information about the beamformable contention period and the non-beamformable contention period, and to transmit the beacon message to the dispersion devices.
 2. The central control unit of claim 1, wherein the source allocation scheduling unit schedules a data transmission period including at least one of the beamformable contention period, the non-beamformable contention period, and a schedule period based on a request for a resource from the dispersion devices.
 3. The central control unit of claim 1, wherein: the beacon message includes allocation information of a time resource indicating an access period, allocation information of a time resource indicating a polling period, and allocation information of a time resource indicating a data transmission period, and the data transmission period includes at least one of the beamformable contention period, the non-beamformable contention period, and a schedule period.
 4. The central control unit of claim 1, wherein the beacon message further includes a contention period participation list including information about dispersion devices participating in the contention period and information related to setting a receiving antenna for each of the dispersion devices participating in the contention period.
 5. A dispersion device for providing contention based channel access in a wideband wireless communication system, the dispersion device comprising: a requesting unit to request a central control unit to participate in a contention period; a beacon processing unit to verify, in a beacon message received from the central control unit, a beamformable contention period corresponding to a contention period during which a beamforming is allowed and a non-beamformable contention period corresponding to a contention period during which the beamforming is interrupted; a beamforming unit to perform beamforming with a dispersion device to communicate in the beamformable contention period; and a data processing unit to process data transmitted to and received from the dispersion device to communicate in the non-beamformable contention period through a beam formed by the beamforming unit.
 6. The dispersion device of claim 5, wherein the requesting unit informs the central control unit of information related to setting a receiving antenna for the dispersion device when the requesting unit requests participation in the contention period.
 7. The dispersion device of claim 5, wherein: the beacon processing unit verifies, in the beacon message, a contention period participation list including information about dispersion devices participating in the contention period and information related to setting a receiving antenna for each of the dispersion devices participating in the contention period, and the beamforming unit performs the beamforming by verifying information related to setting a receiving antenna for the dispersion device to communicate in the contention period participation list.
 8. The dispersion device of claim 5, wherein: the beacon message includes allocation information of a time resource indicating an access period, allocation information of a time resource indicating a polling period, and allocation information of a time resource indicating a data transmission period, and the data transmission period includes at least one of the beamformable contention period, the non-beamformable contention period, and a schedule period.
 9. A dispersion device for providing contention based channel access in a wideband wireless communication system, the dispersion device comprising: a direction detector to measure a receiving direction of a directional signal received during an omnidirectional receiving antenna mode; a duration controller to manage, for each predetermined direction, information of a transmission duration corresponding to a network allocation vector included in a message that is wirelessly received in a state set to the omnidirectional receiving antenna mode; and a media access control (MAC) layer unit to start communication when information of a transmission duration of a predetermined direction managed by the duration controller is “0” by verifying the information of the transmission duration of the predetermined direction for communication in the predetermined direction.
 10. The dispersion device of claim 9, wherein the duration controller verifies the information of the transmission duration in a duration field within a MAC header of the received message.
 11. The dispersion device of claim 9, wherein the duration controller manages the information of the transmission duration along with a transmission address of the received message, a reception address of the received message, and information of a receiving direction of the received message.
 12. A method of providing contention based channel access in a central control unit of a wideband wireless communication system, the method comprising: receiving, from dispersion devices in a network, information about participating in a contention period and information related to setting a receiving antenna; allocating a resource by dividing the contention period into a beamformable contention period corresponding to a contention period in which a beamforming of a directional antenna is allowed and a non-beamformable contention period corresponding to a contention period in which the beamforming is interrupted; and generating a beacon message including information about the beamformable contention period and the non-beamformable contention period, and transmitting the beacon message to the dispersion devices.
 13. The method of claim 12, wherein the allocating comprises scheduling a data transmission period including at least one of the beamformable contention period, the non-beamformable contention period, and a schedule period based on a request for a resource from the dispersion devices.
 14. The method of claim 12, wherein: the beacon message includes allocation information of a time resource indicating an access period, allocation information of a time resource indicating a polling period, and allocation information of a time resource indicating a data transmission period, and the data transmission period includes at least one of the beamformable contention period, the non-beamformable contention period, and a schedule period.
 15. The method of claim 12, wherein the beacon message further includes a contention period participation list including information about dispersion devices participating in the contention period and information related to setting a receiving antenna for each of the dispersion devices participating in the contention period.
 16. A method of providing contention based channel access in a dispersion device of a wideband wireless communication system, the method comprising: requesting a central control unit to participate in a contention period; verifying, in a beacon message received from the central control unit, a beamformable contention period corresponding to a contention period in which a beamforming is allowed and a non-beamformable contention period corresponding to a contention period in which the beamforming is interrupted; performing beamforming with a dispersion device to communicate in the beamformable contention period; and exchanging data with the dispersion device to communicate in the non-beamformable contention period through a beam formed by performing the beamforming.
 17. The method of claim 16, wherein the requesting comprises informing the central control unit of information related to setting a receiving antenna for the dispersion device when requesting the participation.
 18. The method of claim 16, wherein: the verifying comprises verifying, in the beacon message, a contention period participation list including information about dispersion devices participating in the contention period and information related to setting a receiving antenna for each of the dispersion devices participating in the contention period, and the performing comprises performing the beamforming by verifying information related to setting a receiving antenna for the dispersion device to communicate in the contention period participation list.
 19. The method of claim 16, wherein: the beacon message includes allocation information of a time resource indicating an access period, allocation information of a time resource indicating a polling period, and allocation information of a time resource indicating a data transmission period, and the data transmission period includes at least one of the beamformable contention period, the non-beamformable contention period, and a schedule period. 